get_balance

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations already indicate read-only and non-destructive behavior, and the description does not contradict this. It adds valuable insight into the meaning of a zero balance and the resulting 402 error, which goes beyond the basic annotations. It does not describe the exact output format, but that may be covered by the output schema.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is extremely concise—two sentences—and conveys all necessary information without redundant fluff. It is well-structured: first states the core purpose, then adds relevant context about the balance meaning. No filler or vague wording.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple balance-checking tool, the description is complete: it defines the resource, the action, and the interpretation of the result. It also mentions the 402 scenario, which is useful contextual information. It does not discuss authentication or key handling, but those are likely implicit and not required for this tool's use.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has no parameters, so there is nothing to explain. The baseline for zero-parameter tools is 4, and the description does not need to add information about parameters. The description complements the schema by clarifying what the tool returns.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the purpose: retrieving the remaining credits on the user's key. It names the resource (key) and the action (remaining credits), leaving no ambiguity about what the tool does. It is distinct from sibling tools focused on tokens, so no confusion arises.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides useful context on when to interpret the balance (e.g., a balance of 0 means paid tools will return 402), implicitly guiding the user to check balance before using paid tools. However, it does not explicitly state when to prefer this tool over alternatives or when not to use it, though the clear purpose makes this unnecessary.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.